1. Field of the Invention
The invention is concerned with powder peroxide bleach compositions and their formation. More particularly the invention is concerned with powder percarbonate bleach compositions which exhibit relatively long term stability and which retain integrity of composition from the top to the bottom of a box filled therewith.
2. Prior Art
Powder bleach compositions are of course very well known to the prior art. In these compositions attempts have been made to utilize commercial grades of percarbonate having about 10% to 15% available oxygen to provide at least a portion of the available oxygen therein. However, because of the relatively low stability of the percarbonate compounds of the prior art it has generally been necessary to use another peroxide compound, for example sodium perborate or the like in the powder bleach composition to assure that it maintains at least adequate available oxygen level after long term storage. The use of sodium perborate in a bleach composition along with sufficient soda ash to provide a desired alkalinity thereto has lead to a problem in that the sodium perborate dissolves relatively slowly in both warm and cold water as compared to sodium percarbonate. Also, such perborate based bleach compositions have a tendency to cake on standing so that they do not retain a free flowing character for a sufficiently long period of time. Further, such compositions have a tendency to separate on handling and storage whereby a dry bleach composition which originally might have sodium perborate and soda ash uniformly distributed therethroughout can eventually have a concentration of one of these products towards the bottom of a box thereof with a concentration of another of the ingredients towards the top thereof. Such separation occurs because of differences in density, differences in particle size, differences in particle shape and the like. Such separation can also occur in a bleach composition which comprises sodium percarbonate and soda ash if the composition is made by mixing together the two individual components. Further still, a composition of sodium percarbonate and soda ash made by mixing the two components together, as mentioned previously has a relatively low storage stability and exhibits a reduction in available oxygen content with time of storage which is undesirably high.
Accordingly, it is an object of the present invention to provide a powder bleach composition having the active oxygen content thereof supplied by sodium percarbonate.
It is another object of the present invention to provide a powder bleach composition which is resistant to separation.
It is a further object of the present invention to provide a powder bleach composition having sodium percarbonate therein to supply the available oxygen content thereof, which composition exhibits improved storage stability.
Yet another object of the present invention is to provide a powder bleach composition wherein substantially each particle thereof comprises both soda ash and sodium percarbonate so that separation of the composition does not occur on handling or storage.
A still further object of the present invention is to provide a sodium percarbonate powder bleach composition wherein the available oxygen content is more quickly available in solution than in prior art compositions.
Another object yet of the present invention is to provide a process for making a separation resistant dry bleach composition having the advantages stated in the above objects.
These and other objects of the present invention as will become apparent from reading the following specification are accomplished as set out herein.